Polyamic acid composition, polyimide production method, laminate production method, and electronic device production method

Abstract

This polyamic acid composition contains a polyamic acid and organic solvents. The organic solvents include a first organic solvent represented by general formula (1) and a second organic solvent represented by general formula (2). The weight ratio of the second organic solvent to the first organic solvent is 2 / 8 to 8 / 2. In general formula (1), R1, R2, and R3 each independently represent a hydrogen atom or a monovalent organic group having one or more carbon atoms, and at least one of R1, R2, and R3 represents a monovalent organic group having two or more carbon atoms. In general formula (2), R4 represents a monovalent organic group having two or more carbon atoms.　

Description

Polyamic acid composition, method for producing polyimide, method for producing laminate, and method for producing electronic device

[0001] The present invention relates to a polyamic acid composition, a method for producing a polyimide, a method for producing a laminate, and a method for producing an electronic device.The present invention further relates to an electronic device material using the polyimide, a thin film transistor (TFT) substrate, a flexible display substrate, a color filter, a printed matter, an optical material, an image display device (more specifically, a liquid crystal display device, an organic electroluminescence (EL) display, an electronic paper, etc.), a 3D display, a solar cell, a touch panel, a transparent conductive film substrate, and a substitute material for a component currently using glass.

[0002] Rapid advances in electronic devices, such as displays (liquid crystal displays, organic electroluminescence (EL) displays, electronic paper displays), solar cells, and touch panels, have led to devices becoming thinner, lighter, and more flexible. Polyimide is being used as a substrate material in place of glass substrates in these devices.

[0003] These devices require various electronic elements, such as thin-film transistors and transparent electrodes, to be formed on a substrate, and high-temperature processes are required to form these electronic elements. Polyimides have sufficient heat resistance to be adapted to high-temperature processes, and their coefficient of linear expansion (CTE) is similar to that of glass substrates and electronic elements, making them less susceptible to internal stress and suitable for use as substrate materials for flexible displays and other applications.

[0004] The above-mentioned substrate material is produced by applying a solution of polyamic acid (polyamic acid composition) to a support, imidizing the polyamic acid to form a polyimide film, and then laminating electronic elements thereon.

[0005] As a solvent for dissolving polyamic acid, an amide solvent having a relatively small number of carbon atoms, such as N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), or N,N-dimethylacetamide (DMAC), is usually used. However, from the viewpoint of the impact on the environment and the human body, there has been a demand for a change to a solvent with higher safety.

[0006] Known examples of preparing polyamic acid compositions using highly safe solvents include the use of water as a solvent by utilizing a polyamic acid salt (Patent Document 1, etc.), and the synthesis of polyamic acid using an alkoxy-N-substituted propanamide as a solvent with low teratogenicity (Patent Documents 2 and 3, etc.).

[0007] JP 2012-36382 A JP 2017-517582 A International Publication No. 2022 / 054850

[0008] As a result of investigations conducted by the present inventors, it has been found that when the polyamic acid compositions described in Patent Documents 1 to 3 are applied onto a support and the polyamic acid is imidized, the heat resistance of the resulting polyimide is reduced, which may make it difficult to apply the polyimide to applications requiring heat resistance, such as substrates for flexible displays.

[0009] The present invention has been made in view of the above-mentioned circumstances, and aims to provide a polyamic acid composition that can produce a polyimide having excellent heat resistance while using a highly safe solvent, as well as a method for producing a polyimide, a method for producing a laminate, and a method for producing an electronic device using the polyamic acid composition.

[0010] <Aspects of the Present Invention> The present invention includes the following aspects.

[0011] [1] A polyamic acid composition comprising a polyamic acid and an organic solvent, wherein the organic solvent comprises a first organic solvent represented by the following general formula (1) and a second organic solvent represented by the following general formula (2), and the weight ratio of the second organic solvent to the first organic solvent is 2 / 8 or more and 8 / 2 or less:

[0012]

[0013] In the general formula (1), R １ , R ２ and R ３ each independently represents a monovalent organic group having one or more carbon atoms or a hydrogen atom; R １ , R ２ and R ３At least one of R represents a monovalent organic group having two or more carbon atoms, and in the general formula (2), ４ represents a monovalent organic group having two or more carbon atoms.

[0014] [2] The polyamic acid composition according to [1], wherein the first organic solvent is at least one selected from the group consisting of 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-dimethylpropionamide, and N,N-diethylformamide.

[0015] [3] The polyamic acid composition according to [1] or [2], wherein the second organic solvent is at least one selected from the group consisting of 1-ethyl-2-pyrrolidone, 1-vinyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-n-octyl-2-pyrrolidone, and 1-cyclohexyl-2-pyrrolidone.

[0016] [4] The polyamic acid composition according to any one of [1] to [3], wherein the polyamic acid contains 3,3',4,4'-biphenyltetracarboxylic dianhydride residues as tetracarboxylic dianhydride residues, and the content of the 3,3',4,4'-biphenyltetracarboxylic dianhydride residues is 50 mol % or more based on the total tetracarboxylic dianhydride residues constituting the polyamic acid.

[0017] [5] The polyamic acid composition according to any one of [1] to [4], wherein the polyamic acid contains a p-phenylenediamine residue as a diamine residue, and the content of the p-phenylenediamine residue is 50 mol % or more based on the total diamine residues constituting the polyamic acid.

[0018] [6] A method for producing a polyimide, comprising heating the polyamic acid composition according to any one of [1] to [5] above to imidize the polyamic acid.

[0019] [7] A method for producing a laminate having a support and a polyimide film, comprising: applying the polyamic acid composition according to any one of [1] to [5] above onto a support to form a coating film containing the polyamic acid; and heating the coating film to imidize the polyamic acid.

[0020] [8] A method for producing an electronic device, comprising: a step Sa of heating the polyamic acid composition according to any one of [1] to [5] above to imidize the polyamic acid; and a step Sb of arranging an electronic element on the polyimide film obtained by the step Sa.

[0021] According to the present invention, it is possible to provide a polyamic acid composition that can produce a polyimide having excellent heat resistance while using a highly safe solvent, as well as a method for producing a polyimide using the polyamic acid composition, a method for producing a laminate, and a method for producing an electronic device.

[0022] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. In addition, all academic and patent documents described in this specification are incorporated herein by reference.

[0023] First, the terms used in this specification will be explained. A "structural unit" refers to a repeating unit that constitutes a polymer. A "polyamic acid" is a polymer containing a structural unit represented by the following general formula (3) (hereinafter, sometimes referred to as "structural unit (3)").

[0024]

[0025] In general formula (3), A １ represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from a tetracarboxylic dianhydride), A ２ represents a diamine residue (a divalent organic group derived from a diamine).

[0026] The content of the structural unit (3) relative to all structural units constituting the polyamic acid is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, even more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

[0027] The "1% weight loss temperature" is the temperature measured when the weight of the polyimide at a measurement temperature of 120° C. is reduced by 1% by weight relative to the reference weight (100% by weight). The 1% weight loss temperature is measured by the same method as in the examples described below or a method equivalent thereto.

[0028] Unless otherwise specified, the "linear expansion coefficient" refers to the linear expansion coefficient when the temperature is decreasing from 100°C to 450°C.

[0029] The "alkyl group" and "alkoxyalkyl group" are both straight-chain or branched-chain and unsubstituted.

[0030] Hereinafter, the compound name may be followed by "based" to refer to the compound and its derivatives in a comprehensive manner. Furthermore, when the compound name is followed by "based" to represent the name of a polymer, unless otherwise specified, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, tetracarboxylic acid dianhydrides may be referred to as "acid dianhydrides."

[0031] Unless otherwise specified, the components and functional groups exemplified in this specification may be used alone or in combination of two or more kinds.

[0032] A polyamic acid composition according to this embodiment includes a polyamic acid and an organic solvent. The organic solvent includes a first organic solvent represented by the following general formula (1) and a second organic solvent represented by the following general formula (2).

[0033]

[0034] In general formula (1), R １ , R ２ and R ３each independently represents a monovalent organic group having one or more carbon atoms or a hydrogen atom. １ , R ２ and R ３ At least one of R represents a monovalent organic group having two or more carbon atoms. ４ represents a monovalent organic group having two or more carbon atoms.

[0035] In this embodiment, the organic solvent includes one or more first organic solvents and one or more second organic solvents, and the weight ratio of the second organic solvent to the first organic solvent (weight of the second organic solvent / weight of the first organic solvent) is 2 / 8 or more and 8 / 2 or less.

[0036] Hereinafter, the weight ratio of the second organic solvent to the first organic solvent (weight of the second organic solvent / weight of the first organic solvent) may be referred to as the "specific solvent weight ratio."

[0037] Generally, amide solvents with a relatively small number of carbon atoms, such as N,N-dimethylformamide, N-methyl-2-pyrrolidone, and N,N-dimethylacetamide, are used in polyamic acid compositions from the viewpoint of improving solubility and properties, but these solvents have come to be viewed as harmful to health. In contrast, the first organic solvent and the second organic solvent used in the present embodiment have a relatively large number of carbon atoms, and therefore have little impact on the environment and human body and are highly safe.

[0038] On the other hand, the present inventors have found that when a polyamic acid composition containing an organic solvent having a relatively large number of carbon atoms is applied to a support and then imidized, the 1% weight loss temperature of the resulting polyimide film tends to decrease. This is presumably because, during the temperature-raising step of imidization (e.g., when the heating temperature is around 400°C), the organic solvent having a relatively large number of carbon atoms tends to remain in the film (precursor film of the polyimide film). As a result, the residual solvent causes partial decomposition of the polymer, resulting in a decrease in the heat resistance of the resulting polyimide. In contrast, according to the present embodiment, by setting the specific solvent weight ratio within the range of 2 / 8 to 8 / 2, a polyimide with excellent heat resistance can be obtained. The reason for this is presumed to be as follows.

[0039] The first organic solvent used in this embodiment has a relatively low boiling point. Therefore, when only the first organic solvent is used as the organic solvent, the solvent on the film surface tends to evaporate selectively at relatively low temperatures during the temperature-raising step of imidization. Therefore, when only the first organic solvent is used as the organic solvent, the solvent tends to remain inside the film. On the other hand, the second organic solvent used in this embodiment has a relatively high boiling point. When only the second organic solvent is used as the organic solvent, the solvent tends to evaporate less from the entire film during the imidization step, resulting in the solvent remaining inside the film. In contrast, in this embodiment, the first organic solvent and the second organic solvent are used in combination at a specific weight ratio (specific solvent weight ratio). This prevents excessive evaporation of the solvent from the film surface at relatively low temperatures, which is a problem with the first organic solvent, and also eliminates the problem of the second organic solvent, which is the difficulty of evaporating the solvent from the entire film. This reduces the amount of organic solvent remaining during the temperature-raising step of imidization. Therefore, this embodiment provides a polyimide with excellent heat resistance.

[0040] In this embodiment, in order to obtain a polyimide having superior heat resistance, the weight ratio of the specific solvent is preferably 2.5 / 7.5 or more and 7.5 / 2.5 or less, and more preferably 3 / 7 or more and 7 / 3 or less.

[0041] In this embodiment, in order to obtain a polyimide having superior heat resistance, it is preferable to use a first organic solvent having a boiling point of 200°C or higher and 250°C or lower, and it is more preferable to use a first organic solvent having a boiling point of 200°C or higher and 220°C or lower.

[0042] In the present embodiment, in order to obtain a polyimide having superior heat resistance, it is preferable to use a second organic solvent having a boiling point of 210°C or higher and 260°C or lower, and it is more preferable to use a second organic solvent having a boiling point of 221°C or higher and 260°C or lower.

[0043] In the present embodiment, in order to obtain a polyimide having superior heat resistance, the difference in boiling point between the first organic solvent and the second organic solvent is preferably 10°C or more and 60°C or less, and more preferably 20°C or more and 40°C or less.

[0044] In order to obtain a polyimide having improved safety and excellent heat resistance, R １ , R ２ and R ３ are each independently preferably a monovalent organic group having 1 to 8 carbon atoms or a hydrogen atom, more preferably a monovalent organic group having 1 to 6 carbon atoms or a hydrogen atom.

[0045] In order to obtain a polyimide having improved safety and further excellent heat resistance, it is necessary to １ is preferably an alkoxyalkyl group having 2 to 8 carbon atoms, an alkyl group having 2 to 8 carbon atoms, or a hydrogen atom. ２ and R ３ As R in the general formula (1), it is preferable that each independently be an alkyl group having 1 to 8 carbon atoms. １ When R is a hydrogen atom, in order to obtain a polyimide having improved safety and further excellent heat resistance, ２ and R ３ are each independently preferably an alkyl group having 2 to 8 carbon atoms.

[0046] In order to obtain a polyimide having improved safety and excellent heat resistance, R ４ As the alkyl group, a monovalent organic group having from 2 to 10 carbon atoms is preferred, a monovalent organic group having from 2 to 8 carbon atoms is more preferred, a monovalent hydrocarbon group having from 2 to 8 carbon atoms is even more preferred, and an alkyl group having from 2 to 8 carbon atoms is even more preferred.

[0047] In order to obtain a polyimide having excellent heat resistance while improving safety, the first organic solvent is preferably one or more selected from the group consisting of 3-methoxy-N,N-dimethylpropanamide (hereinafter sometimes referred to as "MPA"), 3-butoxy-N,N-dimethylpropanamide (hereinafter sometimes referred to as "BPA"), N,N-dimethylpropionamide (hereinafter sometimes referred to as "DMPA"), and N,N-diethylformamide (hereinafter sometimes referred to as "DEF"), and more preferably MPA.

[0048] In order to obtain a polyimide having excellent heat resistance while improving safety, the second organic solvent is preferably at least one selected from the group consisting of 1-ethyl-2-pyrrolidone, 1-vinyl-2-pyrrolidone, 1-butyl-2-pyrrolidone (hereinafter sometimes referred to as "NBP"), 1-n-octyl-2-pyrrolidone, and 1-cyclohexyl-2-pyrrolidone, and more preferably NBP.

[0049] The polyamic acid composition according to this embodiment may contain an organic solvent other than the first organic solvent and the second organic solvent. However, from the viewpoint of safety, the total content of the first organic solvent and the second organic solvent in the polyamic acid composition according to this embodiment is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, and may even be 100% by weight, based on the total amount (100% by weight) of organic solvents in the polyamic acid composition. Furthermore, from the viewpoint of safety, the content of the amide-based solvents other than the first organic solvent and the second organic solvent in the polyamic acid composition according to this embodiment is preferably 1000 ppm by weight or less, more preferably 500 ppm by weight or less, and even more preferably 100 ppm by weight or less, based on the total amount of organic solvents in the polyamic acid composition.

[0050] In this embodiment, in order to obtain a polyimide having superior heat resistance, the residual solvent content, which will be described later, is preferably 0.10% by weight or less.

[0051] The polyamic acid contained in the polyamic acid composition according to this embodiment (hereinafter, may be referred to as the "specific polyamic acid") has a tetracarboxylic dianhydride residue and a diamine residue.

[0052] In order to obtain a polyimide that is superior in heat resistance and can further reduce internal stress, the specific polyamic acid preferably contains a 3,3',4,4'-biphenyltetracarboxylic dianhydride residue as the tetracarboxylic dianhydride residue. Hereinafter, 3,3',4,4'-biphenyltetracarboxylic dianhydride may be referred to as "BPDA."

[0053] In order to obtain a polyimide that is more excellent in heat resistance and can further reduce internal stress, the content of BPDA residues is preferably 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more, relative to all tetracarboxylic dianhydride residues (100 mol %) constituting the specific polyamic acid, and may be 80 mol % or more, 90 mol % or more, or even 100 mol %.

[0054] In order to obtain a polyimide that has excellent heat resistance and can further reduce internal stress, the specific polyamic acid preferably has a p-phenylenediamine residue as the diamine residue. Hereinafter, p-phenylenediamine may be referred to as "PDA."

[0055] In order to obtain a polyimide that is more excellent in heat resistance and can further reduce internal stress, the content of PDA residues is preferably 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more, relative to all diamine residues (100 mol %) constituting the specific polyamic acid, and may be 80 mol % or more, 90 mol % or more, or even 100 mol %.

[0056] To obtain a polyimide having superior heat resistance and capable of further reducing internal stress, the specific polyamic acid preferably has a BPDA residue as the tetracarboxylic dianhydride residue and a PDA residue as the diamine residue. The specific polyamic acid containing BPDA and PDA residues has a rigid structure, thereby reducing internal stress. However, when the polyamic acid has a rigid structure, the rigid structure is generally less susceptible to thermal vibration during the imidization process, which tends to result in solvent remaining in the film during imidization. In contrast, in this embodiment, the first organic solvent and the second organic solvent are used in combination at a specific weight ratio (specific solvent weight ratio), thereby reducing the amount of organic solvent remaining during the temperature-raising step of imidization. Therefore, according to this embodiment, a polyimide having excellent heat resistance can be obtained even when an organic solvent with a relatively large number of carbon atoms is used with a specific polyamic acid containing BPDA and PDA residues.

[0057] Examples of acid dianhydrides (monomers) that can be used in addition to BPDA when synthesizing a specific polyamic acid include spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone (hereinafter sometimes referred to as "SFDA"), 4,4'-oxydiphthalic anhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, pyromellitic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, and 2,3,6,7-naphthalenetetracarboxylic acid. Acid dianhydride, p-phenylene bis (trimellitate anhydride), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2'-oxodispiro [bicyclo [2.2.1] heptane-2,1'-cyclopentane-3',2''-bicyclo [2.2.1] heptane] -5,6:5'',6''-tetracarboxylic dianhydride and derivatives thereof, which may be used alone or in combination.

[0058] In order to obtain a polyimide having superior heat resistance, it is preferable to use SFDA as the acid dianhydride (monomer). That is, in order to obtain a polyimide having superior heat resistance, it is preferable that the specific polyamic acid has an SFDA residue as the tetracarboxylic dianhydride residue. The SFDA residue is a tetravalent organic group represented by the following chemical formula (4):

[0059]

[0060] In order to obtain a polyimide having even more excellent heat resistance, the content of the SFDA residue is preferably 0.5 mol % or more and 5.0 mol % or less, and more preferably 1.0 mol % or more and 3.0 mol % or less, relative to the total tetracarboxylic dianhydride residues (100 mol %) constituting the specific polyamic acid.

[0061] In order to obtain a polyimide having even more excellent heat resistance, the specific polyamic acid preferably has BPDA residues and SFDA residues as tetracarboxylic dianhydride residues. In order to obtain a polyimide having even more excellent heat resistance, the total content of BPDA residues and SFDA residues is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more, relative to all tetracarboxylic dianhydride residues constituting the specific polyamic acid (100 mol%). It may also be 80 mol% or more, 90 mol% or more, or even 100 mol%.

[0062] When synthesizing a specific polyamic acid, examples of diamines (monomers) that can be used other than PDA include 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereinafter, sometimes referred to as "PAM-E"), 9,9-bis(4-aminophenyl)fluorene, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzanilide, m-phenylenediamine, and 4,4'-oxygen. Examples thereof include dianiline, 3,4'-oxydianiline, N,N'-bis(4-aminophenyl)terephthalamide, m-tolidine, o-tolidine, 4,4'-bis(4-aminophenoxy)biphenyl, 2-(4-aminophenyl)-6-aminobenzoxazole, 3,5-diaminobenzoic acid, 4,4'-diamino-3,3'-dihydroxybiphenyl, 4,4'-methylenebis(cyclohexanamine), and derivatives thereof, and these may be used alone or in combination.

[0063] In order to improve the adhesion between the resulting polyimide film and the glass substrate, it is preferable to use PAM-E as the diamine (monomer).

[0064] In order to obtain a polyimide that has even more excellent heat resistance and can reduce internal stress, the polyamic acid composition according to this embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, even more preferably satisfies the following condition 3, and even more preferably satisfies the following condition 4. Condition 1: The first organic solvent is one or more selected from the group consisting of 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-dimethylpropionamide, and N,N-diethylformamide, and the second organic solvent is one or more selected from the group consisting of 1-ethyl-2-pyrrolidone, 1-vinyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-n-octyl-2-pyrrolidone, and 1-cyclohexyl-2-pyrrolidone. Condition 2: The above condition 1 is satisfied, and the specific polyamic acid contains a BPDA residue and a PDA residue. Condition 3: The above condition 2 is satisfied, and the content of PDA residues is 80 mol % or more relative to all diamine residues (100 mol %) constituting the specific polyamic acid.Condition 4: The above condition 3 is satisfied, and the content of BPDA residues is 80 mol % or more relative to all tetracarboxylic dianhydride residues (100 mol %) constituting the specific polyamic acid.

[0065] The specific polyamic acid can be synthesized by a known general method, for example, by reacting a diamine and a tetracarboxylic dianhydride in an organic solvent. An example of a specific synthesis method for the specific polyamic acid will be described. First, a diamine solution is prepared by dissolving or dispersing a diamine in an organic solvent in an inert gas atmosphere such as argon or nitrogen. Then, a tetracarboxylic dianhydride is dissolved or dispersed in an organic solvent in a slurry state, or the tetracarboxylic dianhydride is added to the diamine solution in a solid state. Another example of a second method is prepared by dissolving or dispersing a tetracarboxylic dianhydride in an organic solvent in an inert gas atmosphere such as argon or nitrogen, or the tetracarboxylic dianhydride is added to the tetracarboxylic dianhydride solution in a solid state. Then, a diamine is dissolved or dispersed in an organic solvent in a slurry state, or the diamine is added to the tetracarboxylic dianhydride solution in a solid state.

[0066] When synthesizing a specific polyamic acid using a diamine and a tetracarboxylic dianhydride, the desired specific polyamic acid (a polymer of a diamine and a tetracarboxylic dianhydride) can be obtained by adjusting the molar amount of the diamine (or, if multiple diamines are used, the molar amount of each diamine) and the molar amount of the tetracarboxylic dianhydride (or, if multiple tetracarboxylic dianhydrides are used, the molar amount of each tetracarboxylic dianhydride). The molar fraction of each residue in the specific polyamic acid corresponds, for example, to the molar fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the specific polyamic acid. Furthermore, a specific polyamic acid containing multiple tetracarboxylic dianhydride residues and multiple diamine residues can also be obtained by blending two types of polyamic acid. The temperature conditions for the reaction between the diamine and the tetracarboxylic dianhydride, i.e., the synthesis reaction of the specific polyamic acid, are not particularly limited, but are, for example, in the range of 20°C to 150°C. The reaction time for the synthesis reaction of the specific polyamic acid is, for example, in the range of 10 minutes to 30 hours.

[0067] The organic solvent used for synthesizing the specific polyamic acid is preferably a solvent capable of dissolving the tetracarboxylic dianhydride and diamine used, and more preferably a solvent capable of dissolving the specific polyamic acid to be produced. From the viewpoint of safety, the organic solvents used for synthesizing the specific polyamic acid are preferably the first organic solvent and the second organic solvent described above. Furthermore, organic solvents other than the first organic solvent and the second organic solvent may also be used for synthesizing the specific polyamic acid. Examples of organic solvents other than the first organic solvent and the second organic solvent include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfoxide-based solvents such as dimethyl sulfoxide; sulfone-based solvents such as diphenyl sulfone and tetramethyl sulfone; amide-based solvents other than the first organic solvent and the second organic solvent, such as N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and hexamethylphosphoric triamide; ester-based solvents such as γ-butyrolactone; alkyl halide-based solvents such as chloroform and methylene chloride; aromatic hydrocarbon-based solvents such as benzene and toluene; phenol-based solvents such as phenol and cresol; ketone-based solvents such as cyclopentanone; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and p-cresol methyl ether. The synthesis reaction of the specific polyamic acid is preferably carried out under an inert gas atmosphere such as argon or nitrogen.

[0068] When a specific polyamic acid is obtained by the above-described method, the reaction solution (the solution after the reaction) itself may be used as the polyamic acid composition according to this embodiment. When the reaction solution itself is used as the polyamic acid composition according to this embodiment, it is preferable to use the above-described first organic solvent and second organic solvent in combination in the above-described specific weight ratio (specific solvent weight ratio) as the organic solvent used to synthesize the specific polyamic acid. Alternatively, the solid specific polyamic acid obtained by removing the solvent from the reaction solution may be dissolved in the first organic solvent and the second organic solvent to prepare the polyamic acid composition according to this embodiment. The content of the specific polyamic acid in the polyamic acid composition according to this embodiment is not particularly limited, but is, for example, 1% by weight or more and 80% by weight or less relative to the total amount of the polyamic acid composition.

[0069] The weight-average molecular weight of the specific polyamic acid varies depending on its application, but is preferably in the range of 10,000 to 1,000,000, more preferably 20,000 to 500,000, and even more preferably 30,000 to 200,000. A weight-average molecular weight of 10,000 or more allows the viscosity of the polyamic acid composition to be easily adjusted to a range suitable for coating (e.g., 0.5 to 10 Pa·s). On the other hand, a weight-average molecular weight of 1,000,000 or less allows the polyamic acid composition to exhibit sufficient solubility in solvents, thereby enabling the production of a coating film or polyimide film with a smooth surface and uniform thickness. The weight-average molecular weight used here refers to a polyethylene oxide equivalent value measured using gel permeation chromatography (GPC).

[0070] Methods for controlling the molecular weight of specific polyamic acids include using an excess of either the acid dianhydride or the diamine, or quenching the reaction by reacting with a monofunctional acid anhydride or amine, such as phthalic anhydride or aniline. When polymerizing with an excess of either the acid dianhydride or the diamine, a polyimide film with sufficient strength can be obtained if the molar ratio of the diamines used to synthesize the specific polyamic acid is between 0.95 and 1.05. The molar ratio is the ratio of the total amount of diamines used to synthesize the specific polyamic acid to the total amount of dianhydrides used to synthesize the specific polyamic acid (total amount of diamines / total amount of dianhydrides). Furthermore, end-capping with phthalic anhydride, maleic anhydride, aniline, or the like can further reduce the coloration of polyimides obtained using specific polyamic acids.

[0071] The polyamic acid composition according to this embodiment may also contain an imidization accelerator and / or a dehydration catalyst in order to shorten the heating time and to develop properties.

[0072] The imidization accelerator is not particularly limited, but a tertiary amine can be used. The tertiary amine is preferably a heterocyclic tertiary amine. Specific preferred examples of heterocyclic tertiary amines include pyridine, picoline, quinoline, isoquinoline, and imidazoles. Specific preferred examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride.

[0073] From the viewpoints of shortening the heating time and of expressing the properties, the amount of the imidization accelerator is preferably from 0.1 to 20 parts by weight, and more preferably from 0.5 to 20 parts by weight, per 100 parts by weight of the specific polyamic acid. Also, from the viewpoints of shortening the heating time and of expressing the properties, the amount of the dehydration catalyst is preferably from 0.1 to 10 parts by weight, and more preferably from 0.5 to 5 parts by weight, per 100 parts by weight of the specific polyamic acid.

[0074] As the imidization accelerator, imidazoles are preferred. In this specification, the term "imidazoles" refers to compounds having a 1,3-diazole ring (1,3-diazole ring structure). Imidazoles that can be added to the polyamic acid composition according to this embodiment are not particularly limited, but examples include 1H-imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole. Of these, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole are preferred, and 1,2-dimethylimidazole and 1-benzyl-2-methylimidazole are more preferred.

[0075] The content of imidazoles is preferably 0.005 mol or more and 0.1 mol or less, more preferably 0.01 mol or more and 0.08 mol or less, and even more preferably 0.015 mol or more and 0.050 mol or less, per mol of amide group in the specific polyamic acid. By incorporating 0.005 mol or more of imidazoles, the film strength and transparency of the polyimide can be improved, and by limiting the content of imidazoles to 0.1 mol or less, the heat resistance of the polyimide can be improved while maintaining the storage stability of the specific polyamic acid. In this specification, the term "amide group of the specific polyamic acid" refers to an amide group formed by the polymerization reaction of a diamine and a tetracarboxylic dianhydride.

[0076] The method for mixing the specific polyamic acid and the imidazole is not particularly limited. From the viewpoint of ease of molecular weight control of the specific polyamic acid, it is preferable to add the imidazole to the specific polyamic acid after polymerization. In this case, the imidazole may be added directly to the specific polyamic acid, or the imidazole may be dissolved in a solvent in advance and this solution may be added to the specific polyamic acid; the addition method is not particularly limited. The polyamic acid composition according to this embodiment may be prepared by adding the imidazole to a solution containing the specific polyamic acid after polymerization (post-reaction solution).

[0077] The polyamic acid composition according to this embodiment may contain various organic or inorganic low-molecular-weight compounds or polymeric compounds as additives. Examples of additives that can be used include plasticizers, antioxidants, dyes, surfactants, leveling agents, silicones, fine particles, and sensitizers. Examples of fine particles include organic fine particles made of polystyrene, polytetrafluoroethylene, and the like, and inorganic fine particles made of colloidal silica, carbon, layered silicates, and the like, which may have a porous or hollow structure. The function and form of the fine particles are not particularly limited, and they may be, for example, pigments, fillers, or fibrous particles.

[0078] Furthermore, the polyamic acid composition according to this embodiment may contain a silane coupling agent to provide appropriate adhesion to the support. Known silane coupling agents can be used without any particular limitation. To provide good adhesion to the support, usable silane coupling agents are preferably compounds containing an amino group, more preferably one or more compounds selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 3-(ethoxydimethylsilyl)propylamine, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and m-aminophenyltrimethoxysilane, even more preferably one or more compounds selected from the group consisting of 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, and m-aminophenyltrimethoxysilane, with m-aminophenyltrimethoxysilane being particularly preferred. The silane coupling agent may be incorporated as a terminal group of the specific polyamic acid.

[0079] The blending ratio of the silane coupling agent to 100 parts by weight of the specific polyamic acid is preferably 0.01 parts by weight or more and 0.50 parts by weight or less, more preferably 0.01 parts by weight or more and 0.30 parts by weight or less. By making the blending ratio of the silane coupling agent 0.01 parts by weight or more, the peeling suppression effect on the support is sufficiently exhibited, and by making the blending ratio of the silane coupling agent 0.50 parts by weight or less, the decrease in the molecular weight of the specific polyamic acid is suppressed, so that the embrittlement of the polyimide film can be suppressed.

[0080] The method for producing a polyimide according to this embodiment includes a step of heating the polyamic acid composition according to this embodiment to imidize the specific polyamic acid. The method for imidizing the specific polyamic acid is not particularly limited, and known methods can be used. An example of a method for imidizing the specific polyamic acid is described below. Imidization is performed by dehydrating and cyclizing the specific polyamic acid. This dehydration and cyclization can be performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. Alternatively, the polyamic acid composition can be directly placed in a container that has been subjected to a release treatment, such as a fluorine-based resin coating, and then heated and dried under reduced pressure to dehydrate and cyclize the specific polyamic acid. Polyimide can be obtained by dehydrating and cyclizing the specific polyamic acid according to these methods. The heating time for each of the above treatments varies depending on the amount of polyamic acid composition to be dehydrated and the heating temperature, but is generally preferably in the range of 1 minute to 300 minutes after the treatment temperature reaches the maximum temperature.

[0081] Furthermore, the imidization of the specific polyamic acid to polyimide can be any ratio between 1% and 100%. In other words, a partially imidized specific polyamic acid may be synthesized. In particular, when imidization is performed by heating, the ring-closing reaction from the specific polyamic acid to polyimide and the hydrolysis of the specific polyamic acid proceed simultaneously, and the molecular weight of the polyimide may be lower than that of the specific polyamic acid. Therefore, from the viewpoint of improving mechanical properties, it is preferable to partially imidize the specific polyamic acid in the polyamic acid composition before forming the polyimide film described below. In this specification, partially imidized polyamic acid may also be referred to as "polyamic acid."

[0082] The method for producing a laminate according to this embodiment is a method for producing a laminate having a support and a polyimide film (specifically, a polyimide film containing an imidized product of a specific polyamic acid). In the method for producing a laminate according to this embodiment, the specific polyamic acid is heated to dehydrate and cyclize the specific polyamic acid, resulting in imidization. The method for heating the specific polyamic acid is not particularly limited, but examples include a method in which the polyamic acid composition according to this embodiment described above is applied to a support to form a coating film containing the specific polyamic acid, and the resulting coating film is then heat-treated at a temperature ranging from 40°C to 500°C. Examples of supports include glass substrates, metal plates, PET films (polyethylene terephthalate films), and glass substrates with a sacrificial layer, in which an amorphous silicon layer (a-Si layer) is laminated on a glass substrate. This method produces a laminate having a support and a polyimide film (specifically, a polyimide film containing an imidized product of a specific polyamic acid) disposed on the support.

[0083] The polyimide content in the polyimide film formed by the above method is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may be 100% by weight, based on the total weight of the polyimide film. Examples of components other than polyimide in the polyimide film include the above-mentioned additives (more specifically, fine particles, etc.).

[0084] The method for producing an electronic device (more specifically, a flexible device, etc.) according to this embodiment includes a step Sa of heating the polyamic acid composition according to this embodiment to imidize the specific polyamic acid, and a step Sb of arranging an electronic element on the polyimide film obtained by step Sa. Step Sa is the same as, for example, the method for producing a laminate according to this embodiment described above. In step Sb, for example, an electronic element (such as a TFT) is directly or indirectly arranged on the polyimide film obtained by step Sa.

[0085] When manufacturing electronic devices for flexible displays, a polyimide film is first formed on an inorganic substrate such as glass as a support. Electronic elements such as TFTs are then arranged (formed) on the polyimide film to form an electronic device on the support. The process of forming TFTs is generally carried out over a wide temperature range of 150°C to 650°C, but to actually achieve the desired performance, oxide semiconductor layers and a-Si layers are formed at 300°C or higher, and in some cases, the a-Si may be further crystallized using a laser or the like.

[0086] In this case, if the thermal decomposition temperature of the polyimide film is low, outgassing may occur during the formation of electronic elements, and the outgassing may adhere to the oven as sublimate, causing contamination inside the oven or peeling of inorganic films (such as the barrier film described below) or electronic elements formed on the polyimide film. Therefore, the 1% weight loss temperature of the polyimide is preferably 500°C or higher, more preferably 550°C or higher, and even more preferably 576°C or higher. The upper limit of the 1% weight loss temperature of the polyimide is preferably as high as possible, but is, for example, 600°C. The 1% weight loss temperature can be adjusted, for example, by changing the content of residues having a rigid structure (more specifically, BPDA residues, PDA residues, etc.). More specifically, before TFT formation, an inorganic film such as a silicon oxide film (SiOx film) or a silicon nitride film (SiNx film) is formed on the polyimide film as a barrier film. In this case, if the polyimide has low heat resistance, if imidization has not progressed completely, or if there is a large amount of residual solvent, the polyimide and the inorganic film may peel off due to volatile components such as decomposition gas of the polyimide during the high-temperature process after lamination of the inorganic film. Therefore, it is desirable that the 1% weight loss temperature of the polyimide is 500°C or higher, and that the weight loss rate when the polyimide is isothermally held at a temperature in the range of 400°C to 450°C is less than 1%.

[0087] Furthermore, if the glass transition temperature (Tg) of the polyimide is significantly lower than the process temperature, misalignment or the like may occur during the formation of electronic elements. Therefore, the Tg of the polyimide is preferably 300°C or higher, more preferably 350°C or higher, even more preferably 400°C or higher, and even more preferably 420°C or higher. The upper limit of the Tg of the polyimide is preferably as high as possible, for example, 470°C. Furthermore, since the linear expansion coefficient of a glass substrate is generally smaller than that of a resin, internal stress occurs between the glass substrate and the polyimide film. If the internal stress of a laminate of a glass substrate or electronic element used as a support and a polyimide film is high, the laminate including the polyimide film will expand during the high-temperature TFT formation process and then shrink when cooled to room temperature, resulting in problems such as warping or breakage of the glass substrate and peeling of the polyimide film from the glass substrate. Therefore, in a laminate having a support and a polyimide film, the internal stress between the polyimide film and the support is preferably 30 MPa or less, more preferably 20 MPa or less, even more preferably 10 MPa or less, and even more preferably 9 MPa or less. The lower limit of the internal stress is the better, and may be 0 MPa. The method for measuring the internal stress is the same as or similar to the method described in the examples below.

[0088] In order to reduce the internal stress between the polyimide film and the support, the linear expansion coefficient of the polyimide film is preferably 30 ppm / K or less, more preferably 20 ppm / K or less, even more preferably 15 ppm / K or less, and particularly preferably 10 ppm / K or less.

[0089] The polyimide obtained by the manufacturing method according to this embodiment can be suitably used as a material for display substrates such as TFT substrates and touch panel substrates. When using polyimide for the above applications, a method is often adopted in which an electronic device (more specifically, an electronic device in which electronic elements are formed on a polyimide film) is formed on a support as described above, and then the polyimide film is peeled off from the support. Furthermore, alkali-free glass is suitably used as the support material. An example of a method for manufacturing a laminate of a polyimide film and a support will be described in detail below.

[0090] First, the polyamic acid composition according to this embodiment is applied (cast) onto a support to form a coating film-containing laminate consisting of a coating film containing the specific polyamic acid and the support. Next, the coating film-containing laminate is heated, for example, at a temperature of 40°C to 200°C. The heating time is, for example, 3 minutes to 120 minutes. A multi-stage heating process may be performed, for example, by heating the coating film-containing laminate at 50°C for 30 minutes and then at 100°C for 30 minutes. Next, to promote imidization of the specific polyamic acid in the coating film, the coating film-containing laminate is heated, for example, at a maximum temperature of 200°C to 500°C. The heating time (heating time at the maximum temperature) is, for example, 1 minute to 300 minutes. It is preferable to gradually increase the temperature from a low temperature to the maximum temperature. The heating rate is preferably 2°C / min to 10°C / min, more preferably 4°C / min to 10°C / min. The maximum temperature is preferably in the range of 250°C or higher and 480°C or lower. If the maximum temperature is 250°C or higher, imidization proceeds sufficiently, while if the maximum temperature is 480°C or lower, thermal degradation and discoloration of the polyimide can be suppressed. The reaction may be maintained at any temperature for any time until the maximum temperature is reached. The imidization reaction can be carried out in air, under reduced pressure, or in an inert gas such as nitrogen. To achieve higher transparency, however, it is preferable to carry out the reaction under reduced pressure or in an inert gas such as nitrogen. Known heating devices such as hot air ovens, infrared ovens, vacuum ovens, inert ovens, and hot plates can be used. Through these steps, the specific polyamic acid in the coating film is imidized, and a laminate of the support and the polyimide film (a film containing an imidized product of the specific polyamic acid) can be obtained.

[0091] The polyimide film can be peeled from the resulting laminate of the support and the polyimide film by known methods. For example, the film may be peeled by hand, or by using a mechanical device such as a drive roll or a robot. Furthermore, a method of providing a peeling layer between the support and the polyimide film, or a method of forming a silicon oxide film on a substrate having a large number of grooves, forming a polyimide film using the silicon oxide film as an underlayer, and then peeling the polyimide film by infiltrating a silicon oxide etchant between the substrate and the silicon oxide film can also be employed. Another method of separating the polyimide film by irradiation with laser light can also be employed.

[0092] Furthermore, in a batch-type device production process in which a polyamic acid composition is applied to a support such as a glass substrate, heated to imidize, and then electronic elements or the like are formed, and the polyimide film is then peeled off, excellent adhesion between the support and the polyimide film is preferred. Here, adhesion refers to adhesion strength. In a production process in which electronic elements or the like are formed on the polyimide film on the support, and the polyimide film on which the electronic elements or the like are formed is then peeled off from the support, excellent adhesion between the polyimide film and the support allows for more accurate formation or mounting of electronic elements or the like. In a production process in which electronic elements or the like are disposed on a support via a polyimide film, from the viewpoint of improving productivity, the peel strength between the support and the polyimide film is preferably 0.05 N / cm or more, and more preferably 0.1 N / cm or more.

[0093] In the above-described manufacturing process, when peeling a polyimide film from a laminate of a support and a polyimide film, the polyimide film is often peeled from the support by laser irradiation. In this case, since the polyimide film needs to absorb the laser light, the cutoff wavelength of the polyimide film is required to be longer than the wavelength of the laser light used for peeling. Since a XeCl excimer laser with a wavelength of 308 nm is often used for laser peeling, the cutoff wavelength of the polyimide film is preferably 312 nm or more, more preferably 330 nm or more. On the other hand, if the cutoff wavelength is long, the polyimide film tends to be colored yellow, so the cutoff wavelength of the polyimide film is preferably 400 nm or less. From the viewpoint of achieving both transparency (low yellowness) and laser peeling processability, the cutoff wavelength of the polyimide film is preferably 320 nm or more and 400 nm or less, more preferably 330 nm or more and 390 nm or less. In this specification, the cut-off wavelength means a wavelength at which the transmittance is 0.1% or less as measured by an ultraviolet-visible spectrophotometer.

[0094] The polyamic acid composition according to this embodiment and the polyimide obtained by the production method according to this embodiment may be used directly in a coating or molding process for producing a product or component, or may be used as a material for further coating a film-shaped molded product, etc. For use in a coating or molding process, the polyamic acid composition or polyimide may be dissolved or dispersed in an organic solvent as needed, and further blended with a photocurable component, a thermosetting component, a non-polymerizable binder resin, and other components as needed to prepare a composition containing the specific polyamic acid or polyimide.

[0095] On the surface of the polyimide film obtained by the manufacturing method according to this embodiment, various inorganic thin films such as a metal oxide thin film, a transparent electrode, etc. The method for forming these inorganic thin films is not particularly limited, and examples thereof include PVD methods such as sputtering, vacuum deposition, and ion plating, and CVD methods.

[0096] The polyimide film obtained by the production method according to this embodiment is heat-resistant, exhibits low internal stress when laminated with a glass substrate, and can ensure adhesion to inorganic materials during high-temperature processes. Therefore, it is preferable for use in fields and products where these properties are valuable. For example, the polyimide film obtained by the production method according to this embodiment is preferably used in image display devices such as liquid crystal displays, organic electroluminescence (EL) displays, and electronic paper, printed materials, color filters, flexible displays, optical films, 3D displays, touch panels, transparent conductive film substrates, solar cells, and the like. It is even more preferable for it to be used as a replacement material for parts currently using glass. In these applications, the thickness of the polyimide film is, for example, from 1 μm to 200 μm, and preferably from 5 μm to 100 μm. The thickness of the polyimide film can be measured using a laser hologram.

[0097] The polyamic acid composition according to this embodiment can be suitably used in a method for producing a polyimide film, which involves applying the polyamic acid composition to a support, heating it to imidize it, and then peeling the polyimide film from the support. The polyamic acid composition according to this embodiment can also be suitably used in a batch-type device production process, which involves applying the polyamic acid composition to a support, heating it to imidize it, forming electronic elements or the like on the formed polyimide film, and then peeling the polyimide film with the electronic elements or the like formed on it from the support. Therefore, the method for producing an electronic device according to this embodiment may include a step of peeling the polyimide film with the electronic elements or the like formed on it from the support.

[0098] Examples of the present invention will be described below, but the scope of the present invention is not limited to the following examples.

[0099] <Methods for Measuring Physical Properties> First, methods for measuring physical properties of polyimide (polyimide film) will be described.

[0100] [Internal Stress] Each polyamic acid composition prepared in the following Examples and Comparative Examples was applied using a spin coater to a Corning glass substrate (trade name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) whose warpage had been measured in advance. The substrate was then heated in air at 80°C for 30 minutes, and then heated in a nitrogen atmosphere at 460°C for 20 minutes to obtain a laminate comprising a 10 μm-thick polyimide film on the glass substrate. To eliminate the influence of water absorption by the polyimide film, the laminate was dried at 120°C for 10 minutes, and the warpage of the laminate was measured at 25°C in a nitrogen atmosphere using a thin film stress measurement device ("FLX-2320-S" manufactured by KLA-Tencor Corporation). The internal stress generated between the glass substrate and the polyimide film was calculated using the Stoney equation from the warpage of the glass substrate before the polyimide film was formed and the warpage of the laminate.

[0101] [Coefficient of Linear Expansion (CTE)] The CTE of the polyimide film peeled from each laminate obtained in the Examples and Comparative Examples described below was measured by the tensile load method using a thermal analyzer ("TMA / SS7100" manufactured by Hitachi High-Tech Science Corporation) with a load of 29.4 mN applied to the long side of the polyimide film. Specifically, the polyimide film (width 3 mm, length 10 mm) was heated from 20°C to 470°C at a heating rate of 10°C / min in a nitrogen atmosphere, and then cooled to 20°C at a cooling rate of 15°C / min. The CTE was calculated from the strain from 100°C to 450°C during cooling.

[0102] [1% Weight Loss Temperature (TD1)] A polyimide film (specifically, a polyimide film sampled to a weight of 10 mg) sampled from each laminate obtained in the Examples and Comparative Examples described below was used as a measurement sample. Using a simultaneous differential thermal and thermogravimetric analyzer ("TG / DTA7200" manufactured by Hitachi High-Tech Science Corporation), the temperature was raised from 25°C to 650°C at a rate of 10°C / min under a nitrogen atmosphere. The sample weight at a measurement temperature of 120°C was used as the reference, and the measurement temperature at which the weight decreased by 1% by weight relative to this reference weight was defined as the 1% weight loss temperature (TD1). When TD1 was 576°C or higher, the sample was evaluated as having "excellent heat resistance." On the other hand, when TD1 was less than 576°C, the sample was evaluated as having "poor heat resistance."

[0103] [Residual Solvent Content] Each polyamic acid composition prepared in the following Examples and Comparative Examples was applied to a Corning glass substrate (trade name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) using a spin coater and heated in air at 80°C for 30 minutes to obtain a precursor film for forming a polyimide film. The obtained precursor film was then peeled off from the glass substrate and heated from 120°C to 460°C at a rate of 7°C / min in a nitrogen atmosphere using a differential thermal and thermogravimetric simultaneous analyzer (Hitachi High-Tech Science Corporation, "TG / DTA7200") to obtain a 10 μm-thick polyimide film. During the heating process to obtain the polyimide film, the content of organic solvent remaining in the film at the time when the temperature reached 400°C (residual solvent content) was calculated using the following formula: Residual solvent content (unit: wt%) = 100 × (weight loss of film between 400°C and 460°C) / (weight of film when reaching 400°C - weight loss of film between 400°C and 460°C)

[0104] <Preparation of Polyimide Film> The methods for preparing polyimide films (laminates) in the Examples and Comparative Examples are described below. In the following, compounds and reagents are abbreviated as follows. The polyamic acid compositions used to prepare the polyimide films were all prepared under a nitrogen atmosphere. MPA: 3-methoxy-N,N-dimethylpropanamide (boiling point: 215°C) NBP: 1-butyl-2-pyrrolidone (boiling point: 241°C) BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride SFDA: spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone PDA: p-phenylenediamine MAPTMS: m-aminophenyltrimethoxysilane

[0105] Example 1 First, 70 parts by weight of MPA and 30 parts by weight of NBP were mixed as the polymerization organic solvent to obtain a mixed solvent S1. The resulting mixed solvent S1 (weight: 41.6 g) was placed in a 300 mL glass separable flask equipped with a stainless steel stirrer and a nitrogen inlet tube. Next, while stirring the contents of the flask, 2.687 g of PDA was added to the flask and dissolved. Next, 0.152 g of SFDA and 7.161 g of BPDA were added to the flask, and the contents were stirred for 4 hours under an atmosphere at 85°C. Next, 0.025 g of MAPTMS was added to the flask, and the contents were stirred for 4 hours under an atmosphere at 40°C to obtain a polyamic acid composition. The obtained polyamic acid composition was applied to a Corning glass substrate (trade name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm × 100 mm) using a spin coater, and the applied coating was heated in air at 80°C for 30 minutes, and then heated in a nitrogen atmosphere at 460°C for 20 minutes to obtain a laminate (laminate of Example 1) comprising a 10 μm-thick polyimide film on the glass substrate.

[0106] [Example 2, Example 3, and Comparative Examples 1 to 4] The laminates of Example 2, Example 3, and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the weight ratio of MPA to NBP in the organic solvent (mixed solvent) for polymerization was changed as shown in Table 1.

[0107] Example 4 A laminate of Example 4 was obtained in the same manner as in Example 2, except that MAPTMS was not added.

[0108] Table 1 shows the weight ratio of MPA to NBP in the mixed solvent used for Examples 1 to 4 and Comparative Examples 1 to 4, the acid dianhydrides used and their charge ratios, the diamines used and their charge ratios, the amount of MAPTMS added, the residual solvent content, as well as the internal stress, CTE, and TD1. In Table 1, a "-" indicates that the corresponding component was not used. In Table 1, the values ​​in the "Acid Dianhydride" column represent the content (unit: mol%) of each acid dianhydride relative to the total amount (100 mol%) of diamines used. In Table 1, the values ​​in the "Diamine" column represent the content (unit: mol%) of each diamine relative to the total amount (100 mol%) of diamines used. In Table 1, the values ​​in the "MAPTMS" column represent the amount (unit: parts by weight) of MAPTMS used relative to 100 parts by weight of polyamic acid.

[0109] Furthermore, in all of Examples 1 to 4 and Comparative Examples 1 to 4, the molar fraction of each polyamic acid residue in the prepared polyamic acid composition was consistent with the molar fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the polyamic acid. Furthermore, in all of Examples 1 to 4 and Comparative Examples 1 to 4, the weight ratio of MPA to NBP (specific solvent weight ratio) in the obtained polyamic acid composition was consistent with the weight ratio of MPA to NBP in the mixed solvent used.

[0110]

[0111] The polyamic acid compositions used in Examples 1 to 4 had a specific solvent weight ratio of 2 / 8 or more and 8 / 2 or less. As shown in Table 1, the TD1 values ​​were 576°C or more in Examples 1 to 4. Therefore, the polyimide films obtained in Examples 1 to 4 had excellent heat resistance.

[0112] The polyamic acid composition used in Comparative Example 1 did not contain a second organic solvent. The polyamic acid composition used in Comparative Example 2 did not contain a first organic solvent. The polyamic acid compositions used in Comparative Examples 3 and 4 had specific solvent weight ratios outside the range of 2 / 8 or more and 8 / 2 or less. As shown in Table 1, in Comparative Examples 1 to 4, TD1 was less than 576°C. Therefore, the polyimide films obtained in Comparative Examples 1 to 4 did not have excellent heat resistance.

[0113] The above results demonstrate that the present invention can provide a polyamic acid composition that can be used to produce a polyimide having excellent heat resistance while using a highly safe solvent.

Claims

1. A polyamic acid composition comprising a polyamic acid and an organic solvent, wherein the organic solvent comprises a first organic solvent represented by the following general formula (1) and a second organic solvent represented by the following general formula (2), and the weight ratio of the second organic solvent to the first organic solvent is 2 / 8 or more and 8 / 2 or less. (In the general formula (1), R １ , R ２ and R ３ each independently represents a monovalent organic group having one or more carbon atoms or a hydrogen atom; R １ , R ２ and R ３ At least one of R represents a monovalent organic group having two or more carbon atoms, ４ represents a monovalent organic group having two or more carbon atoms.

2. The polyamic acid composition of claim 1, wherein the first organic solvent is at least one selected from the group consisting of 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-dimethylpropionamide, and N,N-diethylformamide.

3. The polyamic acid composition of claim 1, wherein the second organic solvent is at least one selected from the group consisting of 1-ethyl-2-pyrrolidone, 1-vinyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-n-octyl-2-pyrrolidone, and 1-cyclohexyl-2-pyrrolidone.

4. The polyamic acid composition according to claim 1, wherein the polyamic acid contains 3,3',4,4'-biphenyltetracarboxylic dianhydride residues as tetracarboxylic dianhydride residues, and the content of the 3,3',4,4'-biphenyltetracarboxylic dianhydride residues is 50 mol % or more based on the total tetracarboxylic dianhydride residues constituting the polyamic acid.

5. The polyamic acid composition according to claim 1, wherein the polyamic acid has a p-phenylenediamine residue as a diamine residue, and the content of the p-phenylenediamine residue is 50 mol % or more based on the total diamine residues constituting the polyamic acid.

6. A method for producing a polyimide, which comprises heating the polyamic acid composition according to claim 1 to imidize the polyamic acid.

7. A method for producing a laminate having a support and a polyimide film, comprising applying the polyamic acid composition according to claim 1 onto a support to form a coating film containing the polyamic acid, and heating the coating film to imidize the polyamic acid.

8. A method for manufacturing an electronic device, comprising: a step Sa of heating the polyamic acid composition according to claim 1 to imidize the polyamic acid; and a step Sb of arranging an electronic element on the polyimide film obtained by the step Sa.

Images